For example, say I have a loop of some recorded drums
at 120 BPM. I would
like to know exactly how long the audio sample must be to match 120BPM,
rather then trial and error.
this is really easy. i would not even call this math ;-)
with samplerate R, 1 sec = R samples
at x BPM, 1 min = 60 sec = x beats. so the duration of 1 beat = 60/x sec
combined: 1 beat = R*60/x samples.
so at 120 BPM, 44100 Hz, 1 beat == 22050 samples. but you probably want your
loops to be 4 beats, so 88200 samples.
maarten